Data & methodology

CarCompare separates what is official, what you entered, what is calculated and what is estimated. Every value carries one of these labels. When we do not know something, it is shown as Unknown — never filled in with a guess.

Data sources

RDW data describes the registration, not the mechanical condition or service history of a car. RDW does not record engine code, gearbox, trim or factory options, so CarCompare asks you for these instead of assuming them. RDW responses are cached for up to 12 hours and the raw response is kept for audit.

Ownership-cost formulas (version ownership-1.2.0)

• Depreciation = purchase price − expected resale value. Or, with a yearly rate r over n years: purchase × (1 − (1 − r)ⁿ).
• Fuel = distance ÷ 100 × L/100 km × price per litre.
• LPG = LPG distance ÷ 100 × LPG L/100 km × LPG price + LPG distance ÷ 100 × petrol used while on LPG × petrol price + petrol-only distance ÷ 100 × petrol L/100 km × petrol price.
• Electricity = distance ÷ 100 × kWh/100 km × effective price, where effective price = Σ (share × price) over home, public AC and DC fast charging. If consumption is measured by the car (at the battery), it is divided by the charging efficiency to include charging losses. Official WLTP figures are measured at the socket and already include them.
• Plug-in hybrid: electric share and fuel share of distance are calculated separately with the two formulas above.
• Road tax: calculated per quarter over the ownership period (see below), or your own amount if you prefer.
• LPG conversion: the one-off conversion cost is added, the car is then taxed as an LPG car with a G3/R115 installation and fuel is calculated with the LPG formula. The LPG consumption starts at petrol × 1.2 (LPG holds less energy per litre) and can be edited.
• Recurring costs (insurance, maintenance allowance, APK, tyres, parking, tolls, other) = amount × number of periods.
• Financing = interest of an annuity loan during the ownership period + fees.
• Per month = total ÷ (years × 12); per week = total ÷ (years × 52.1775); per km = total ÷ total distance.

Money is calculated with exact decimal arithmetic and stored in whole euro cents. Each line item is rounded once, half-up.

Road tax (motorrijtuigenbelasting)

Calculated exactly as the law prescribes, from the registered weight, fuel and your province. Per quarter:

1. The weight (massa rijklaar) is rounded to the nearest 100 kg; exactly 50 kg rounds down.
2. National part = base tax for that weight + a fuel surcharge (diesel; LPG/CNG — reduced when a G3, R115 or factory installation is registered; other fuels). Petrol, petrol hybrids and electric cars pay no fuel surcharge.
3. Diesels whose registered particulate emission is above 5 mg/km pay 19% extra on the national part. Without a registered value, diesels first registered before 1 September 2009 are presumed to be above the limit.
4. Provincial part = provincial base for that weight × the opcenten of your province.
5. Fully electric and hydrogen cars pay a percentage of both parts: 70% in 2026–2028, 75% in 2029, full tax from 2030.
6. The total is rounded down to whole euros. Cars of 40 years and older are exempt.

Rates after 2027 have not been published yet; until they are, the latest rates are used and the result says so. Not modelled: campers, the quarter rate for pre-1988 petrol cars, wheelchair installations and business exemptions. You can always check an amount with the Belastingdienst calculator.

APK history and odometer

RDW publishes every APK inspection since 2 June 2022 (date, new expiry date, defects found) and an overall odometer judgement (logisch / onlogisch), but not the km readings themselves. Only RDW can say whether a specific reading is logical: its free kentekencheck compares it with the last reading registered for the plate, which is not published as open data. CarCompare therefore never calls a reading logical on its own. It links to the RDW check and lets you record RDW's answer; meanwhile it marks a reading not logical when RDW's history verdict is “onlogisch” or it is below the advertised reading, and doubtful when the average since first registration is below 3,000 or above 40,000 km a year (a typical Dutch car does about 12,500).

Points to check

• From RDW: open recalls (with RDW's description and remedy), APK status, insurance, export and the odometer verdict for this exact car.
• Known for this model: long-known problems of an engine or gearbox family (e.g. wet timing belts, chain stretch, dual-clutch judder), from manufacturer campaigns and consistent reports by owners and independent workshops. RDW has no engine code, so they are matched on make, model, engine size, fuel and year and marked “likely”. They are a checklist, not a diagnosis.
• Type and age: e.g. battery health for EVs, the particulate filter for a diesel driven few km, rust on older cars.

LPG suitability

Diesel and electric cars cannot be converted. For petrol cars the registry cannot tell whether the engine has direct injection, needs hardened valve seats or has room for a tank — so the verdict is “likely possible” or “check with an installer” (small, three-cylinder or hybrid engines), never a guarantee.

Estimates for everything RDW does not give

Every calculator field starts with a realistic value for the exact car, marked Estimate with a note on how it was made. Typing your own number replaces it. No AI is used for these:

• Fuel prices: today's average Dutch pump prices from CBS (80416ned).
• Fuel / electricity use: the official RDW figure × 1.15 (WLTP) or × 1.35 (NEDC) for real-world driving; without a figure, estimated from the weight. Plug-in hybrids: use with an empty battery from the weight; electric share from the real electric range vs your daily distance.
• Purchase price (without an advert): list price when new × typical value left after its age (−20% in year 1, then −12% a year). Depreciation: 15% a year under 3 years, 12% up to 8, then 8%.
• Insurance: by estimated value (third-party, limited or all-risk cover) and power. Maintenance: by powertrain, brand class and age. APK: €40 per test at the legal interval. Tyres: a set by weight class every 40,000 km (EV 32,000). Repair reserve: by age.
• With AI research switched on, owner-reported real-world consumption is offered next to the estimate, and the LPG verdict is based on owner and installer reports for the engine.

Three scenarios

• Best case: fuel and electricity 10% cheaper than your prices, confirmed repairs and scheduled maintenance only.
• Expected: your prices + possible repairs weighted by their probability (only where you have a reliable probability) + your optional repair reserve.
• Worst case: fuel and electricity 10% dearer + the possible repairs you selected at full cost + your repair reserve. It is a plausible bad case, not the sum of every imaginable failure.
• Amounts you enter yourself (insurance, road tax, parking …) are the same in all three.

A repair is counted only once per component: a confirmed repair replaces a scheduled or predicted item for the same component, and a scheduled item replaces a predicted one. Missing inputs are listed and are never treated as €0.

Comparisons

All cars in a comparison use the same kilometres per year, ownership period and energy prices. A ranking is only shown when every car has complete inputs. The plain-language findings are generated from the computed numbers only.

Reproducibility

Every result shows the calculation version and a fingerprint of its inputs. Saved comparisons store the inputs and results verbatim and are shown exactly as saved, even if formulas change later.

Limitations of this version

• No verified maintenance schedules, part fitment or live part prices yet — those require licensed data.
• Insurance and resale value are your inputs.
• No reliability or failure-probability data is shown, because no statistically defensible source is connected.
• Energy price defaults are example values, not live prices.
• Results are research estimates, not inspections or workshop quotations.